Circuit breaker



Feb. 9, 1954 R. c. INGWERSEN CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed Feb. 5, 1952 INVENTOR RICHARD C- \NGWERSEN d gjmm ATTORNEY Feb. 9, 1954 Filed Feb. 5, 1952 R. C. INGWERSEN CIRCUIT BREAKER 2 Sheets-Sheet 2 INVENTOR RICHARD C- INGWERSEN ATTORNEY Patented Feb. 9, 1954 CIRCUIT BREAKER Richard C. Ingwersen, Jackson, Mich., assignor to Mechanical Products, Inc., Jackson, Mich., a

corporation of Michigan Application'February 5, 1952, Serial No. 269,988

Claims. 1

The present invention relates to improvements in electrical switch and circuit breaker constructions, particularly manually operated on-and-ofi switches having current overload protection and involving an automatic circuit breaking action 1 .1 the occurrence of a predetermined current overload.

In the prior Patent No. 2,485,736 in my name and patented October 25, 1949, there is disclosed an electric on-and-off manually resettable circuit breaker in which the latching action of a bimetallic thermal latch is relied upon to maintain the movable contact means of the circuit breaker in closed position against the fixed con tact means. In this prior construction the thermal latch engages an abutment surface, to hold the movable contact means in closed position with respect to the fixed contact means, and slides edgewise with respect to such surface during engagement therewith and disengagement therefrom, while spring means, stressed when the latch engagement is effected, urges the latch into its edgewise contact with the abutment surface.

It is a requirement of these thermal latch cir cuit breakers that the thermal element should be capable of being finely calibrated to suit a specific current rating. This introduces the need for careful selection of the material and of the construction of the thermal element, such as would be facilitated if the considerations involved could be centered merely about the particular current rating and thermal characteristics, to the exclusion of considerations as to wear properties to satisfy the engagement of the thermal element with the abutment surface of the prior constructions and the above stated sliding movement.

It is an object of the invention to provide an electric circuit breaker incorporating a thermal control element which is relieved of any direct latching action and is merely required to bring about the actuation of separate latch means upon the occurrence of a predetermined current overload.

Another object of the invention is to provide an electric circuit breaker incorporating a thermal element in electrical connection with the movable contact means and operable upon current overload to actuate a separate and mechanical latch device, which previously held these contact means in closed relation with respect to their fixed contactv means.

It is yet another object of the invention to provide an electric circuit breaker in which a thermally responsive element for controlling the breaking of the circuit is merely required to partake of expansion movement to bring about the breaking of the controlled circuit and is relieved of the direct latching action of the prior art constructions.

These and further objects and advantages of the invention residing in the construction, arrangement and combination of parts will be more fully understood and will become apparent from a consideration cat the following description with reference to the drawings and from. the appended claims. 8

In the drawings:

Fig. l" is a side elevational view, with one of the molded casing sections removed and looking upon the circuit breaker mechanism mounted in the other casing section, with that mechanical latch part which is carried upon the removed casing. section shown dotted in position,

Fig. II is an end. view, partly in section, through the circuit breaker of Fig. I, with the two casing sections assembled, and

Fig. III is a similar View to Fig. I but with the other casing section removed.

In the drawings, H3, [2 indicate two similar molded casing sections of insulating material mounted together, as by screw-bolts (not shown), to define a hollow interior M, in which the electrical contact assembly and the circuit breaker mechanism are mounted.

The electrical contacts are indicated at Iii. They are carried upon conductor strips l8 retained in recesses in the casing sections and having external terminal posts 26.

The movable electrical contacts are indicated at 22 and are incorporated in the circuit breaker mechanism. There are a pair of fixed contacts and a pair of movable contacts corresponding thereto, as shown, but this is not essential except to the particular embodiment illustrated in the drawings.

The movable contacts 22 are carried upon the outer ends of substantially rigid conductor arms 24 mounted at their inner ends upon a block 26 of insulating material. This block is formed to be s'lidably mounted upon an actuator plunger 28, shown as of flattened bar formation, and carrying an insulated actuator button 3! upon an insulated end portion 32 of the actuator plunger, which portionis slidably mounted in an insulated boss 35 held fixed in one end wall of the casing and having integral ear portions 38. At its op posite end, the plunger 28 is shown formed with three :forh prongs 38 which are slidably supported in the corresponding casing end wall and are slidably guided in corresponding slots in the block 26. A coil spring 40 operates to urge the actuator plunger 28 to the release position in which the button 30 is projected farther to the right than as seen in the drawings to cause the portion 32 to be exposed to view and, by being rendered in some distinctive color such as red, reveal that the circuit has been broken.

The insulated block 26, besides carrying the movable contacts 22, also carries a bimetallic thermal element 42 and a slide 44 fixedly mounted in the block and slidably mounted upon the fiat bar portion of the actuator plunger 28.

The thermal element has a U-shape portion, located on one side of the block, and inturned end portions 4% engaged over one end of the block and secured thereto, as by rivets 48. The slide 44 has lateral ear portions 50 to which one end of a pair of coil springs 52 is attached, the opposite ends of these springs being attached to the cars 36 of the fixed insulator boss structure 34.

The base of the U-shaped thermal element 42 has a plate 54 secured thereto, as by rivets 56, and carries a central screw 58 for a purpose to be described later.

The actuator plunger 28 carries a latch fork element, indicated generally at Gil. This element is pivoted upon the plunger at 62 and has its legs 64, 85 disposed upon opposite sides of the plunger. This fork element forms one part of a mechanical latch mechanism, a companion part of which is mounted upon the inside of the casing section it and is indicated generally at 68.

The fork leg 66 is disposed in adjacent proximity to the screw 58 and is biased towards this screw, as by the action of spring is, so that the other fork leg, having a lug i2, is constantly urged against one side of the slide with the lug positioned to engage over one end of the slide for moving the slide (and hence the movable con-- tacts 22 and thermal element 42) in the contact closing direction. The leg 54 has an enlarged outwardly directed end portion 14 which lies in the path of a portion 78 cf the other latch member 68, which latch member 68 is constantly urged against the leg 64, as by the action of the spring arm 18. When engaged with fork leg 64, as seen in Fig. III, this latch member 68 (fixed on the casing section ill, as stated) serves to retain the movable contacts in closed position against the 1 action of the springs 52.

The slide 44 has lateral flanges 80 projecting from opposite sides thereof and contacting a coil spring 82 mounted. within the block 26. Upon movement of the actuator plunger 28 to close the contacts 2?. the flanges 80 exert pressure against the spring 82, which pressure acts upon the arms 24 carrying the movable contacts and thereby assists in maintaining the desired contact closing pressure.

With the parts as shown in the drawings, the unit, composed by the block 25, slide 44, thermal element 42, rigid arms 24 and movable contacts 22, is held in the Contact closed position, due to the engagement of the latch portion '56 behind the enlarged end portion 14 of the latch leg 64. The unit has been advanced into this position, when the actuator button til was depressed and by the pushing action exerted upon the slide 44 by the engagement of the lug H on the latch leg 64 with the end of the slide 44, it being appreciated that the latch fork 60 is carried upon the plunger actuator 28 and that the lug is constantly urged into the engaging position with respect to the slide by the action of the spring 10, assisted by the spring I8. As this unit is advanced, together with the actuator plunger 28, in the contact closing direction the coil springs 52 are stressed, and at the same time the coil springs 40 and 32 are also stressed. During its passage past the latch member 68 the enlarged latch portion 14 will cam past the latch portion 16, with further tensioning of the spring 18, and an immediate snapping of the latch portion 16 into retaining position behind the said enlarged latch portion 14 when this camming action is completed.

As stated, the thermal element 42 is in electrical series connection with the circuit control contacts and is subject to heating-up as the current flow continues and will be responsive to the heat of overload current. The low expansion side of the element is located on the side adjacent the fork leg 66, with respect to which the inner end of the screw 58, on the thermal element, lies in close proximity in the condition of the element as seen in Fig. III.

Upon the occurrence of overload current the thermal element will deflect inwards and cause the inner end of the screw to exert pressure against the leg 66 of the fork latch member 60. This pressure rocks the member 89 about its pivot 52 on the actuator and will remove the lug i2 from engagement with the slide 44 against the action of the springs 10 and 18. The instant the lug E2 is disengaged from the slide the stressed coil springs 52 operate to move the slide rapidly to the contact open position and thereby efiect the desired circuit breaking action. This will occur even if pressure is applied to the actuator button 30, so that the breaker operates with a trip-free action. In the event that the button is not held depressed at the time when the trip free action occurs the spring 40 will operate to return the actuator plunger to the reset position and thereby position the slide 44 for re-engagement by the latch part 72. The actuator plunger is, in any case, restored to the reset position by the action of the spring 40. Upon movement of the slide in the contact opening direction the spring 82 is de-energized and thus conditioned for further stressing to apply pressure to the movable contact assembly when the contacts are again closed.

It will be appreciated that with the present circuit breaker construction the thermal element 42 is relieved of any latching action, and that its construction may depend entirely upon the current flow characteristics and requirements involved. The construction permits exceedingly fine calibration to be effected, together with the ability for final adjustment to be effected upon laboratory test. To this end the casing section ii! is provided with an opening which, upon assembly of the parts within the casing, and prior to testing, is left open but is eventually closed and sealed, as by the screw plug 84. Prior to the aihxing of this plug in position the head of the screw 58 is accessible for actuation by a screw driver to thereby adjust the initial clearance between the inner end of the screw 58 and the latch leg 68. In this way it is possible to vary the amount of movement and pressure necessary of application to the leg 66 to disengage the latch part 62 from the slide 44. It is thus readily possible to efiect a final calibration by testing the circuit breaker under laboratory conditions. Thereafter, the casing opening would be sealed to prevent unauthorized tampering from taking place.

Having thus described the invention in one practical form but without limitation to the specific details of construction and arrangement thereby involved what I claim as novel and wish to protect by Letters Patent is as follows:

1. In an electric circuit breaker having current overload protection, supporting structure, an actuator plunger reciprocable upon said supporting structure, movable electrical contact means on said actuator plunger, fixed electrical contact means on said structure, said actuator plunger being movable in one direction to engage said movable contact means with said fixed contact means, bi-rnetallic structure in electrical connection with said movable contact means, said bi-metallic structure having a free end deformable by the heat of the conducted current, means mounting said movable contact means and bimetallic structure for movement as a unit relatively to said actuator to disengage said contacts, and mechanical latch mechanism comprising a part on said actuator plunger and a part on said supporting structure, said parts being interengageable to hold said unit in the contact engaged position, said bi-metallic structure being disconnected from said latch mechanism but having its said free end located adjacent one of said latch parts in position to disengage said latch parts when the bi-metallic structure is deformed under the heat of current of a predetermined value.

2. In an electric circuit breaker having current overload protection, supporting structure, an actuator plunger reciprocable upon said supporting structure, movable electrical contact means on said actuator plunger, fixed electrical contact means on said structure, said actuator plunger being movable in one direction to engage said movable contact means with said fixed contact means, bi-metallic structure in electrical connection with said movable contact means, said bi-metallic structure having a free end deformable by the heat of the conducted current, means mounting said movable contact means and bimetallic structure for movement as a unit relatively to said actuator to disengage said contacts, spring means connecting said unit with said supporting structure, said spring means being tensioned when said unit is moved to contact engaged position, and mechanical latch mechanism comprising a part on said actuator plunger and a part on said supporting structure, said parts being inter-engageable to hold said unit in the contact engaged position, said bimetallic structure being disconnected from said latch mechanism but having its said free end located adjacent one of said latch parts in position to disengage said latch parts when the bi-metallic structure is deformed under the heat of current of a predetermined value, said spring means being operative to move said unit to immediately disengage said contacts upon disengagement of said latch parts.

3. In an electric circuit breaker having current overload protection, supporting structure, an actuator plunger reciprocable upon said supporting structure, movable electrical contact means on said actuator plunger, fixed electrical contact means on said structure, said actuator plunger being movable in one direction to engage said movable contact means with said fixed ,contact means, bi-metallic structure in electrical connection with said movable contact means, said bi-metallic structure having a free end deformable by the heat of the conducted current, means mounting said movable contact means and bi-metallic structure for movement as a unit relatively to said actuator to disengage said contacts, spring means connecting said unit with said supporting structure, said spring means being tensioned when said unit is moved to contact engaged position, separate spring means constantly urging said actuator plunger in the contact open direction, and mechanical latch mechanism comprising a part on said actuator plunger and a part on said supporting structure, said parts being inter-engageable to hold said unit in the contact engaged position, said bi-metallic structure being disconnected from said latch mechanism but having its said free end located adjacent one of said latch parts in position to disengage said latch parts when the bi-metallic structure is deformed under the heat or current of a predetermined value, said spring means being operative to move said unit to immediately disengage said contacts upon disengagement of said latch parts.

4. An electric circuit breaker as claimed in claim 3, said latch mechanism comprising a part pivotally mounted on said actuator plunger and engageable with said unit, and a part pivotally mounted on said supporting structure, and spring means cooperable with said latch parts to normally urge said parts into engaged relation with one another and with said unit.

5. An electric circuit breaker as claimed in claim 3, said latch mechanism including a part pivotally mounted on said actuator plunger and having a free end located adjacent said free end of the said bi-metallic structure, said latch part also having a second free end, said second free end being engageable with said unit to hold the unit in the contact engaged position and said other latch part being resiliently engaged with said second free end to hold said free end engaged with said unit while permitting automatic disengagement by pressure applied to said first free end by the said free end of the bi-metallic structure.

RICHARD C. INGWERSEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,485,736 Ingwersen Oct. 25, 1949 2,548,825 Schwend et al Apr. 10, 1951 FOREIGN PATENTS Number Country Date 482,822 Great Britain Apr. 4, 1938 

